Recently techniques have become available for the non-invasive stimulation of the human cortex and human spinal cord. A device has been manufactured which produces a high voltage, extremely brief, pulse which can penetrate skull and activate central nervous system without excessive pain. Previous studies have shown it useful in some circumstances where evaluation of the speed and integrity of motor pathways is valuable. We have just begun to use this technique. Our first project is to see if we can map the motor cortex.